The present invention relates to a thin film magnetic head, a magnetic thin film used as a magnetic core of the thin film magnetic head, and a method for fabricating the magnetic thin film.
A thin film magnetic head according to the present invention is suitable to be incorporated into a magnetic disk unit in a computer.
A thin film magnetic head according to the present invention has both write and read functions, and is applicable to a thin film magnetic head used for both write and read operation.
In a magnetic core material of a conventional thin film magnetic head, permalloy which refers to binary alloys comprising approximately 80 weight percent of nickel and approximately 20 weight percent of iron is used. Since this material has a magnetostriction constant close to zero and high permeability at high frequency regions, a thin film magnetic head using this magnetic core has excellent readout performance.
Since permalloy has a saturation flux density as low as approximately 1 tesla, a thin film magnetic head using permalloy is inferior in writing performance for high recording density. To be concrete, a high coercive force material tends to be used as a material of a recording medium in a magnetic disk unit from the viewpoint of a raised recording density. Further, the thickness of the front end of a thin film magnetic head, i.e., the pole thickness tends to be made small. Therefore, the saturation flux density of 1 tesla of permalloy causes an insufficient magnetic field intensity for writing operation, resulting in insufficient writing performance.
Magnetic disk units tend to increase more and more in capacity and increase in recording density as well therewith.
In a large-capacity magnetic disk unit of 20 gigabytes or more, the core material of the thin film magnetic head is desired to have a higher saturation flux density than that of permalloy. Further, it is demanded to have soft magnetic properties and the uniaxial anisotropy in the same way as permalloy, a small coercive force, a magnetostriction constant close to zero, and excellent corrosion resistance.
As described in JP-A No. 61-76642, a ternary cobalt-nickel-iron alloy thin film investigated by the present inventors with an electroplating method is a material nearly satisfying the above described demands. It is possible to endow the ternary cobalt-nickel-iron alloy thin film with soft magnetic properties and uniaxial anisotropy by alternately applying magnetic fields, which are in parallel to the film surface and perpendicular to each other, when the film is formed.
The present inventors confirmed that a magnetic core comprising a ternary cobalt-nickel-iron alloy thin film fabricated by using a plating method had poor heat resistance and its magnetic characteristic changed under the influence of heat generated in the magnetic head fabrication process. To be concrete, the present inventors confirmed that uniaxial anisotropy and the soft magnetic properties were adversely affected and the coercive force became large. The present inventors also confirmed that if an alloy film of a composition range exhibiting a fine magnetic characteristic in a plated film, i.e., an alloy film comprising 60 to 90 weight percent (59.6 to 86.8 atomic percent) of Co, 10 to 30 weight percent (10.2 to 29.9 atomic percent) of Ni, and 3 to 10 weight percent (3.2 to 10.5 atomic percent) of Fe was fabricated by using a sputtering method, the heat resistance could be improved, but the magnetic characteristic was significantly deteriorated.